This invention is directed to the field of bicycle-type transmission systems, more particularly to a system that includes a pinion gear plate assembly for transferring rotational power to the pinion gears on a pinion shaft, where the system hereof is intended as a replacement to the conventional sprockets and chain drive mechanism.
The present invention relates to a unique transmission system for a cycle type vehicle, such as a bicycle, where the cycle type vehicle comprises a pedal rotary member in driving communication with a driven wheel or wheels. The basic design of standard bicycles has not changed significantly over a number of years. Typically, such standard bicycle is provided with a single sprocket for transmitting chain power from the pedal powered cranks to the rear or driven wheel. Although this configuration is mechanically simple and easy for the operator to control, it possesses the disadvantage that traveling over hilly or uneven terrain can be difficult. Specifically, the rider cannot shift to a lower gear ratio to promote easier travel over such terrain.
To improve mobility, bicycles have employed chain and multi-sprocket type transmissions for several years. Typically, they include an array of sprockets mounted on both the pedal driving and rear driven shafts, where a current system is a ten-speed bicycle. These sprockets offer the rider a selectable choice of drive ratios thereby allowing the rider to tailor the drive to his or her own level of comfort or ability. The chain which transfers power from the driver to the driven shaft is shifted by means of a xe2x80x9cderailleurxe2x80x9d mechanism which moves the chain laterally from sprocket to sprocket. Although this drive system is highly efficient, light weight, cost effective and simple, it nevertheless possesses a number of tangible short-comings and disadvantages.
One such disadvantage, for example, is the relative complexity of the derailleur type transmission. Each lateral movement of the chain from one sprocket to another requires a corresponding compensation in the length of the chain. This unfortunately necessitates the use of a self-adjusting type tensioner which adds further complexity to the design. Moreover, any slight misalignment of the cable driven front and rear derailleur mechanisms can create an inefficient xe2x80x9cbetween gearsxe2x80x9d condition.
To overcome this disadvantage, the prior art has attempted to develop modified power transmission systems for bicycles, where such attempts are illustrated and described in the following U.S. Patents:
U.S. Pat. No. 6,158,296, to Denance, teaches a transmission comprising a gear assembly for transmitting a rotary motion from a driving shaft to a driven shaft, with variable gear ratio where the two shafts and are not coaxial. This transmission consists of a gear-wheel axially split into two half-gear wheels and one axially mobile relative to the other, and also relative to one of the shafts supporting them. The two half-gear-wheels are fixed in rotation relative to this shaft. Additionally, a plate, integral with the other shaft, comprises on at least one of its surfaces several gear teeth, concentric with this shaft, cooperating with the gear-wheel, and elements for axially displacing the two half-gear-wheels to alter the geared concentric tooth, thereby shifting the gear ratio;
U.S. Pat. No. 5,924,950, to Pusic, discloses a transmission for transmitting power from an input shaft to a driving wheel and changing rotating speed ratios. The transmission comprises a drive shaft, a set of drive gears, a driven shaft, a set of driven gears, one counter gear, one return gear including a hub, a planetary gear and sprocket assembly, and a braking mechanism which alternates the operation of the planetary gear. By alternately engaging the different drive gears, the transmission enables the change of an input rotating speed and by stopping the ring gear in the planetary assembly it further multiplies the change of the input rotating speed. Within a very compact and user-friendly design, the transmission provides a full range of speeds and enables smooth power flow resulting in the decrease of power loss in pedal propelled vehicles;
U.S. Pat. No. 5,622,081, to Clements, relates to a multiple speed shaft drive for a bicycle, including a forward disk having a plurality of concentrically disposed ring gears, wherein the forward disk is connected with the pedal crank of the bicycle; a rearward disk having a plurality of concentrically disposed ring gears, wherein the rearward disk is connected to the rear wheel tub; a forward drive shaft; a rearward drive shaft; a free wheel mechanism connecting the forward drive shaft to the rearward drive shaft; a forward pinion gear slidably mounted to the forward drive shaft; a rearward pinion gear slidably mounted to the rearward drive shaft; a forward gear shift mechanism for moving the forward pinion gear into gearing engagement with a selected ring gear of the forward disk; a rearward gear shift mechanism for moving the rearward pinion gear into gearing engagement with a selected ring gear of the rearward disk; and a clutch mechanism which automatically disengages the rearward hub from gearing engagements with the rearward pinion gear whenever a gear shift is made with a shift control operated by the cyclist;
U.S. Pat. No. 5,496,049, to Escobedo, is directed to a drive mechanism for a cycle vehicle for selectively importing a driving force from a pedal operated front gear drive section to a rear gear driven section via a variable transmission. The drive section and the driven section include a plurality of concentric circular rows of gear teeth selectively engageable by front and rear intermediate gears positionable on linear guide rods by a variable combination of manually settable transmission gears. The drive and driven section gears constitute shift gears adapted to achieve gear speed change and provide a driving force to the rear wheel via rotating shafts;
U.S. Pat. No. 5,251,504, to Summerville, Jr. et al., teaches an automatic transmission for driving a rotating wheel having an axle mounted onto a support frame, especially a bicycle frame. The transmission comprises a power input means such as a dual crank-pedal mechanism attached to the frame for receiving power input along with a drive shaft. A plurality of driving elements are mounted for rotation freely about the drive shaft and have engagement means such as sprockets on the surface thereof, one of the driving elements being a lead driver connected to the drive shaft for driving rotation in one direction along with the drive shaft, the driving elements being located at successively greater distances along the shaft from the axle with the lead driver being the farthest from the axle. A drive plate is coupled to the rotating wheel and has on its surface a plurality of concentrically arranged engagement means such as holes which mate with the sprockets on the driving elements for transmitting rotational power from the drive shaft to the drive plate. Means are provided for transferring torsional thrust between the plurality of driving elements and for applying an axial load to the plurality of driving elements along the drive shaft;
U.S. Pat. No. 4,976,348, to Berry, discloses a changeable speed gear attachment for bicycles, including the first gear for interconnection with the front sprocket of a standard bicycle, and a second gear for interconnection with the rear sprocket of a standard bicycle. Shifting means, comprising a plurality of gears and an associated shift lever and transmission cable, are provided. The device may be mounted on the rear frame members of the bicycle without modification of the frame, and the device may be used with bicycles having either a standard chain transmission or a direct-drive chainless transmission; and,
U.S. Pat. No. 4,961,719, to Wildermuth, relates to a drive transmission for a work producing mechanism, such as a bicycle or other vehicle, in which a carrier member is mounted on a rotatable crank shaft, and has a plurality of spaced, pivotally mounted segments, with each segment carrying a rotatable drive element, such as a chain-engageable sprocket. An endless, flexible member, such as a roller chain, is coupled with the sprocket, each segment being in mesh with a free-wheeling gear rotatably mounted on the crank shaft. A chain takeup damper is carried in spaced relationship to the crank shaft and applies tension to a part of the chain at all times. As torque requirements on the crank shaft increase, the other part of the chain increases in tension causing the sprockets to be rotated toward the crank shaft to increase the drive ratio of the transmission. A resilient endless flexible band biases the segments outwardly of the crank shaft and into a maximum drive ratio. A servo system can be used to cause changes in the drive ratio which are dependent upon crank shaft speed instead of torque on a crank shaft.
While the foregoing prior art offer a number of systems for replacing the conventional power transmissions for bicycles, for example, such systems are generally complex and do not offer the simplicity of the present invention. The manner by which this invention improves upon the prior art will become more apparent in the description which follows, particularly when read in conjunction with the accompanying drawings.
This invention is directed to a unique power transmission system for cycle type vehicles, such as bicycles. The cycle type vehicle features, in part, a frame mounting a pedal rotating member, a driven rear wheel, optionally a driven front wheel, and a transmission assembly extending between said pedal rotating member and said driven wheel(s). The transmission assembly comprises a generally circular housing having a pair of spaced apart side faces separated by a peripheral wall, where the housing includes a pinion gear plate rotatable within said housing. The pinion gear plate is rotatable about a shaft having a pair of oppositely oriented pedal arms, each mounting a pivotal pedal for rotatable movement by the vehicle operator. The pinion gear plate features a plurality of gear teeth openings or recesses arranged in a series of concentric rings from the periphery of the plate towards the shaft. Within the housing and cooperating with the openings or recesses in the pinion gear plate is one or a pair of radically oriented cluster assemblies and shifting mechanisms, where a given cluster assembly includes a plurality of pinion gears and clutch assemblies, one for each concentric ring of openings or recesses in the pinion gear plate, a power driving shaft from the mechanism to a driven wheel, and a means to engage or disengage a selected gear with a sliding shifting mechanisms. For driving the rear wheel an inflexible driveshaft mounting a like transmission drive assembly is preferred, while a flexible power transmission shaft is preferred for the optional driven front wheel mounting a like transmission drive assembly. Means are provided for remotely engaging the pinion gear clutch mechanism by the operator, where said pinion gears and clutch assemblies are mounted on a rotatable pinion shaft having a series of concentric slots encircling about the diameter of the pinion shaft, where said clutch mechanism includes a clutch hub which houses a plurality of spring biased pins for engaging said slots of the pinion shaft, where the pins of the clutch mechanism are pushed inward into the slots in the pinion shaft by an encircling and constricting band acted upon by the sliding mechanism.
Accordingly, a feature of this invention is the provision of a unique environmentally sealed and internally lubricated power transmission system for a cycle type vehicle, such as a bicycle, that offers the operator the choice of selected speeds without the complexities of conventional transmission systems.
Another feature of the invention is the use of a rotary pinion gear plate and cooperating cluster assembly and shifting mechanism mounted within a housing, where the pinion gear plate features a plurality of openings or recesses, arranged within plural concentric rings, and said cluster assembly shifting mechanism selectively cooperates with said openings or recesses to allow for differing speeds.
A further feature hereof includes a shifting mechanism having a sliding member with a pair of angled camming slots, where clutch shifting pins move along said camming slots to effect opening and closing of an encircling ring to selectively engage or lock the clutch of the desired pinion gear to the pinion shaft for powering the driven wheel.
These and other features of the invention will become more apparent from the following description, especially when read by those skilled in the art.